Production of hydrogen for use in coal liquefaction

ABSTRACT

A method for producing the hydrogen required in liquefying coal to provide aromatic products such as benzene and naphthalene. The method includes the steps of contacting hydrogen produced in the process with coal in a liquefaction zone and refining the hydrocarbon liquefaction product, which includes polycyclic aromatics, polycyclic hydroaromatics and alkylaromatics, by contacting the liquefaction product with steam and a steam dealkylation catalyst in order to react the hydrocarbons and steam to provide hydrogen and the aromatic products. The aromatic products are recovered from the resulting liquids and the hydrogen thus produced is passed to the coal liquefaction step.

United States Patent 1 [11] 3,925,188 Lester 5] Dec. 9, 1975 1 PRODUCTION OF HYDROGEN FOR USE IN COAL LIQUEF AC TION [75] lnventor: George R. Lester, Park Ridge, [11. [73] Assignee: Universal Oil Products Company, Des Plaines, Ill.

[22] Filed: Jan. 17, 1974 [2!] Appl. N0.: 434,153

Related US. Application Data [63] Continuation-impart of Ser. No, 236,771, March 22,

I972, abandoned.

[52] US. Cl 208/8; 260/672 R [51] Int. Cl. CIOG l/04 [58] Field of Search 208/8, 9, 10; 260/672 R [56] References Cited UNITED STATES PATENTS 3,436,433 4/1969 Lester 260/672 R 3,477,94] ll/l969 Nelson 203/8 3,642,927 2/l972 Kovach et al 260/674 3,649,706 3/1972 Lester 260/672 R Primary Examiner-Delbert E. Gantz Assistant Examiner-James W. Hellwege Attorney, Agent, or Firm-James R. Hoatson, Jr.; Thomas K. McBride; William H. Page, II

[57] ABSTRACT I gen and the aromatic products. The aromatic products are recovered from the resulting liquids and the hydrogen thus produced is passed to the coal liquefaction step.

6 Claims, N0 Drawings PRODUCTION OF HYDROGEN FOR USE IN COAL LIQUEFACTION CROSS-REFERENCE TO RELATED APPLICATIONS A BACKGROUND OF THE INVENTION This invention relates to a process for producing hydrogen for use in coal liquefaction. This invention further relates to a process for producing aromatic hydrocarbons in a hydrogen-consuming operation for the liquefaction of coal which employs hydrogen derived from reacting steam and coal liquefaction products. This invention further relates to the use of steam dealkylation conditions and catalysts to convert coal liquefaction products into hydrogen and valuable aromatic hydrocarbons.

Various methods have been suggested for converting coal into more valuable liquid hydrocarbons, primarily in order to provide substitutes for petroleum-derived hydrocarbons. Coal liquefaction methods include, for example, destructive hydrogenation and solvent extraction. A major drawback to the commercialization of such prior art coal liquefaction methods has been the unavailability of a suitable source of hydrogen. Hydrogen is generally required in large quantities in known coal liquefaction methods. There has been, however, no economical source of hydrogen available to provide the substantial amounts of hydrogen needed in order to enable liquefaction of coal to become commercially practical. Prior art methods for refining hydrocarbonaceous liquefaction products derived from coal are generally analogous to methods for the refining of petroleum residuals. These refining methods have invariably stressed the need for the consumption of hydrogen in all phases of coal liquids processing. For example, in desulfurization, hydrotreating, etc., of coal liquids, large quantities of hydrogen are consumed, in addition to the substantial amounts of hydrogen consumed in the initial coal liquefaction step itself; Another example of a hydrogen-consuming refining process which requires consumption of large amounts of hydrogen is hydrodealkylation of alkylaromatic hydrocarbons to provide aromatic hydrocarbons. in order to reduce the amount of hydrogen required in a given coal liquefaction process, it has been proposed in the art to limit the fraction of coal which is liquefied to that relatively small fraction of the coal which is inherently rich in hydrogen. It is, however, more desirable to convert as large a fraction of the coal as possible into valuable hydrocarbon liquids. Heretofore, this has been uneconomical because of the lack of available extraneous hydrogen. Thus, a large fraction of the coal which could otherwise be liquefied to produce valuable products has been left unconverted to liquids, not because of the difficulty of converting the coal to liquid form, but because of adverse economic factors associated with the hydrogen consumption in the liquefaction operation. There is an apparent need for a coal liquefaction process which provides an economical method for converting essentially all the carbonaceous materials in coal to valuable hydrocarbon products without the necessity for obtaining large extraneous amounts of hydrogen for use in liquefaction. Theabove noted problem associated with obtaining hydrogen for use in coal liquefaction has been aggravated by the necessity for obtaining further large amounts of hydrogen when prior art hydrogen-consuming processes, such as desulfurization, are employed to refine the coal liquefaction products to provide commercially desirable products such as benzene. The disadvantages of these prior art attempts to provide valuable products from coal are obviated by the process of this invention.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for deriving valuable liquid hydrocarbon products from coal without the use of extraneous hydrogen.

Another object of the present invention is to provide an economical method for producing the hydrogen requirements in a coal liquefaction process.

A further object of the present invention is to provide a method for refining coal liquids without resort to a hydrogen-consuming refining operation.

Another object of the present invention is to provide a combination coal liquefaction and coal liquids refining process wherein all hydrogen requirements in the liquefaction step are supplied by the refining step.

Another object of the present invention is to provide a coal liquefaction and refining operation which provides relatively pure, valuable aromatic hydrocarbon products, such as benzene and naphthalene.

ln an embodiment, the present invention relates to a process for producing hydrogen for use in liquefying coal to provide an aromatic hydrogen for use in liquefying coal to provide an aromatic hydrocarbon product, which process comprises the steps of: contacting coal with hydrogen, comprising a hydrogen recycle stream derived as hereinafter specified, in a liquefaction zone at liquefaction conditions; separating the effluent from the liquefaction zone into a solids phase, a first liquid hydrocarbons phase and a first gaseous phase, the first liquid hydrocarbons phase and a first gaseous phase, the first liquid hydrocarbons phase comprising polycyclic aromatic hydrocarbons, polycyclic hydroaromatic hydrocarbons and alkylaromatic hydrocarbons, and removing at least a portion of the solids phase and the first gaseous phase from the process; contacting at least a portion of the first liquid hydrocarbons phase with steam and with a steam dealkylation conditions, whereby at least a portion of the polycyclic aromatic hydrocarbons, the polycyclic hydroaromatic hydrocarbons and the alkylaromatic hydrocarbons are reacted with steam to form hydrogen and the aromatic hydrocarbon product; separating at least a portion of the effluent from the dealkylation zone to provide a second gaseous phase and a second liquid hydrocarbons phase comprising the aromatic hydrocarbon product, and recovering the aromatic hydrocarbon product from the second liquid hydrocarbons phase; and, recovering the hydrogen recycle stream from the second gaseous phase and passing the hydrogen recycle stream into the liquefaction zone.

I have found that, by subjecting the hydrocarbon liquefaction product obtained from a hydrogen-consuming coal liquefaction operation to steam dealkylation conditions in the presence of a steam dealkylation catalyst it is possible to react the coal liquefaction products with steam to generate the complete hydrogen requirement needed for the coal liquefaction step, while sim ultaneously producing valuable aromatic hydrocarbon products such as benzene and naphthalene. It is thereby possible, utilizing the process of the present invention, to generate substantially all the hydrogen required for coal liquefaction using only the hydrocarbon liquefaction product and abundantly available water. This results in the complete satisfaction of the hydrogen input requirements for the coal liquefaction step without resort to expensive, extraneous sources of hydrogen. Refining of the coal liquefaction product to provide valuable aromatic products such as benzene and naphthalene is also thereby accomplished without resort to hydrogen-consuming refining operations using expensive, extraneous hydrogen, such as hydrodesulfurization.

Further objects, embodiments and advantages of the process of the present invention are more fully set forth in the detailed description of the invention provided hereinafter.

DETAILED DESCRIPTION OF THE INVENTION The process of the present invention may be applied to convert any naturally occurring carbonaceous solid to valuable aromatic products, although the process is particularly applicable to the conversion of coal to provide aromatic hydrocarbons. Among the naturally occurring carbonaceous materials which may be converted by the present process are, in addition to coal, peat, oil shale, tar sand, etc. The use of carbonaceous materials other than coal may not give results equivalent to that obtained when coal is utilized. The present invention is particularly applicable to the conversion of bituminous coals, and preferably bituminous coals having a relatively high volatiles content. For example, a bituminous coal having a volatiles content of greater than about weight percent is preferred.

The hydrogen-consuming liquefaction step in the present process may employ any conventional hydrogen-consuming liquefaction technique known in the art. For example, destructive hydrogenation, in which coal is contacted with hydrogen at high temperatures and pressures, is a suitable method for performing the liquefaction step in the present process. Another liquefaction technique which is well known in the art, and which is the preferred method for performing the liquefaction step in the present process, is solvent extraction.

In a preferred embodiment of the liquefaction step utilizing solvent extraction of the coal, coal is pulverized sufficiently to pass through about a 100 mesh sieve, or finer. Coal ground sufficiently fine to pass through a 200 mesh sieve is particularly preferred for use. The comminuted coal is contacted with the required amount of hydrogen which is supplied from the refining step hereinafter described. The coal and hydrogen are contacted with a conventional hydrocarbonaceous liquefaction solvent at a pressure of about 200F. to about l000F., preferably for a time sufficient to dissolve about 70 weight percent of the coal, or more. The liquefaction zone in the present process may be any conventional coal liquefaction reactor used in the art. The liquefaction step may be carried out in a batch-type operation or a continuous-type operation. Preferably, a continuous operation is performed, in which comminuted coal, hydrogen and the solvent are continuously admixed and passed into the liquefaction reactor and the effluent from the liquefaction reactor is continuously recovered and treated in a conventional manner to separate out and recover the hydrocarbon liquefaction product. Conventional solvents may be employed in the solvent extraction step. Solvents which have hydrogen donor properties, such as tetrahydronaphthalene, decahydronaphthalene, etc., are preferred. Another preferred type of solvent for use in the liquefaction step in the present process is a hydrocarbon or mixture of hydrocarbons obtained from the coal liquids. A portion, fraction or derivative of the hydro carbons recovered after the liquefaction step, after the processing of the liquefaction zone effluent by hydrogenation, and/or after the refining of the liquefaction product in the dealkylation zone described hereinafter, may also be utilized. By employing a solvent derived from the process of the present invention, the expense of providing an extraneously produced solvent for use in the liquefaction step is avoided. It is, however, possi' ble to use extraneously provided solvents with good results. In addition to the above noted hydrogen donor solvents, various extraneous solvents which are useful include residual petroleum fractions such as slurry oils, vacuum tower bottoms, etc.

In addition to elevated temperatures and pressures in a preferred embodiment of the present process employing solvent extraction in the liquefaction step, the solvent and coal are contacted at a solvent/coal weight ratio of about l:5 to about lOzl. When using tetrahydronaphthalene or a similar preferred solvent, a solvent/coal weight ratio of about 1:1 to about 5:1 is preferred. A residence time in the liquefaction zone of about 1 minute to about l20 minutes is also preferred.

Hydrogen required in the liquefaction step is provided by utilization of a hydrogen recycle stream produced in the subsequent refining step in which the liquefaction product is treated at steam dealkylation conditions as hereinafter described. The amount of hydrogen needed in the liquefaction step may vary depending on the exact liquefaction procedure employed in a particular embodiment and also depending upon whether the liquefaction step includes further hydrogen treating of the coal liquids before passing the liquid phase hydrocarbons obtained in the liquefaction step to the hydrogen-producing refining step. When the preferred solvent extraction type of liquefaction is utilized, good results have been obtained by employing from about 5 moles to about 25 moles of hydrogen per kilogram of combined coal and hydrocarbonaceous solvent passed into the liquefaction zone. When using preferred operational liquefaction temperatures between about 300C. and about 500C, a hydrogen pressure of about atmospheres to about atmospheres is maintained in the liquefaction zone by continuous addition of hydrogen recycled from the refining step. The effluent from the liquefaction zone is conventionally a mixture of solids, liquids and gases. The solids consist primarily of inorganic coal ash along with some undissolved carbonaceous material. The liquid phase fraction of the liquefaction zone effluent is a conventional mixture of coal liquefaction products, primarily polycyclic aromatic and alkylaromatic hydrocarbons such as naphthalene, alkylnaphthalenes, anthracene, alkylanthracenes, etc., along with some polycyclic hydroaromatic and alkyl substituted hydroaromatic hydrocarbons such as tetrahydronaphthalene, dihydrophenanthrene, dihydroanthracene, and the alkyl derivatives thereof, as well as a lesser amount of alkylaromatics such as toluene, polymethylbenzenes, methylethyl substituted benzenes, ethylbenzene, polyethylbenzenes, etc. Those skilled in the art will recognize that the mixture of liquid hydrocarbons obtained by liquefaction of coal, using conventional hydrogen-consuming liquefaction techniques such as solvent extraction, contains primarily polycyclic aromatic hydrocarbons, but also contains variable amounts of a large number of hydrocarbon compounds, depending on the type of coal used, the liquefaction temperature employed, the type of solvent, etc. The gaseous effluent from the liquefaction zone comprises unreacted hydrogen mixed with small amounts of steam, hydrogen sulfide, etc., which result from the liquefaction step. The liquid hydrocarbon phase is separated from the gaseous phase and solids phase by any conventional method. The gaseous phase is preferably separated by simple flash distillation. Hydrogen contained in the gaseous phase is preferably purified by conventional techniques and recycled to the liquefaction zone for further use. The solids phase in the liquefaction zone effluent may be separated from the liquids phase by conventional methods such as settling, filtration, centrifugation, etc.

When the preferred liquefaction procedure, solvent extraction, is utilized, it may be desirable to hydrogen treat the liquid hydrocarbons recovered from the solvent extraction operation. It may also be desirable to hydrogen treat any hydrocarbonaceous liquefaction solvents or any hydrocarbon fraction to be used subsequently as a liquefaction solvent. When it is desired to thus treat the liquid phase hydrocarbons obtained from the liquefaction procedure, the hydrogen employed for the hydrogen treatment is obtained from the hereinafter described refining step. it may be desirable to hydrogen treat the liquid phase obtained from the liquefaction operation, either before or after separation of the liquid phase from the solids phase and the gaseous phase with which it is admixed in the liquefaction zone effluent. This hydrogen treatment has been found to reduce polymerization, eliminate sulfur and nitrogen contaminants, etc. The hydrogen treatment also facilitates the conversion of the liquids in the subsequent refining step by reacting at least a portion of the polycy" clic aromatic hydrocarbons in the liquid phase to provide hydroaromatic hydrocarbons. For example, a fraction of the phenanthrene present in the liquefaction zone effluent may be converted by the hydrogen treatment into dihydrophenanthrene. The more highly saturated polycyclic compounds are more easily converted in the subsequent refining step to provide hydrogen for use in the liquefaction step and to provide benzene and naphthalene products. This optional hydrogen treatment is performed by contacting the liquid hdyrocarbons phase with hydrogen and, generally, with a hydrogenation catalyst at a temperature of about 300C. to about 500C. and a pressure of about 50 atmospheres to about 700 atmospheres. The amount of hydrogen which must be supplied in the hydrogen treatment from the subsequent refining step is from about standard cubic feet to about 250 standard cubic feet per kilogram of the liquid hydrocarbon phase which is to be treated. Catalysts which are useful in the hydrogen treatment are well known in the art and include, for example, oxides and sulfides of iron, nickel, cobalt and molybdenum. The hydrogen treatment is preferably undertaken in a continuous type of operation. The catalyst can be mixed with the liquid phase hydrocarbons as a slurry after the coal liquids are separated from the solids and gaseous phases. The slurry is passed into a conventional reactor in upward or downward flow with provision for intimate contact between the slurry and the hydrogen gas supplied from the refining step described below. The catalyst may be separated from the hydrogen treated liquid hydrocarbons phase by settling, distillation, etc. The unconsumed hydrogen recovered from the hydrogen treatment operation may be purified and recycled either to the liquefaction operation or to the hydrogen treatment operation for further use.

irrespective of whether the liquid hydrocarbons phase produced in the liquefaction zone is hydrogen treated as described above or is simply recovered from admixture with the solids and gaseous phases in the liquefaction zone effluent, the liquid hydrocarbons phase is then passed into the second, refining stage of the process, wherein a steam dealkylation catalyst and steam dealkylation conditions are employed to produce the total amount of hydrogen required in the above described liquefaction operation and the optional hydrogen treatment of the coal liquid, if utilized, and to provide benzene and naphthalene as products of the process. It is intended that the liquefaction step in the present process includes both the liquefaction of the solid coal and, if desired, the further hydrogen treatment of the liquid hydrocarbons phase produced in the liquefaction operation as described above.

ln the refining step, the liquid hydrocarbons phase recovered from the liquefaction step is contacted with steam and with a steam dealkylation catalyst in a conventional steam dealkylation zone. A variety of conventional reactors suitable for use in the refining step will be obvious to those skilled in the art. In the refining step, steam is contacted with the liquid hydrocarbons phase and with a steam dealkylation catalyst at a steam/hydrocarbons weight ratio between about 2:1 and about 30:1. Preferably, a steam/hydrocarbon weight ratio between about 5:1 and about 20:1 is utilized in the steam dealkylation zone. Steam dealkylation conditions employed in the coal liquids refining step include a temperature between about 300C. and about 600C. and a pressure of about atmospheric to about 10 atmospheres. The liquid hydrocarbons phase may be contacted with steam and a steam dealkylation catalyst in a batch type or continuous type operation. Preferably, a continuous, fixed bed operation is utilized, wherein a fixed bed of steam dealkylation catalyst is maintained in a conventional steam dealkylation reactor, the liquid hydrocarbons phase and steam are commingled at a steam/hydrocarbon weight ratio of about 5:1 to about 20:1 and the steam-hydrocarbon mixture is continuously passed into the steam dealkylation reactor across the fixed catalyst bed, and then withdrawn from the dealkylation reactor. When a continuous operation is employed, the steam-hydrocarbon mixture is passed through the steam dealkylation reactor at a hydrocarbon liquid hourly space velocity (total volume of liquid phase hydrocarbons charged to the steam dealkylation reactor per hour divided by the total volume of steam dealkylation catalyst in the reactor) of about 0.1 to about 10. A liquid hourly space velocity for hydrocarbons charged to the steam dealkylation reactor between about 0.1 and about 2 is preferred. The polycyclic aromatic hydrocarbons, polycyclic alkylaromatic hydrocarbons, hydroaromatic hydrocarbons and alkylaromatic hydrocarbons which are contained in admixture in the liquid hydrocarbons phase charged to the steam dealkylation zone are reacted therein with steam to form hydrogen and aromatic hydrocarbon products, primarily benzene, along with some naphthalene. For example, a mole of hy' droaromatic hydrocarbons such as dihydroanthracene reacts to form hydrogen and 2 moles of benzene. Alkylnaphthalene reacts to form naphthalene and hydrogen, etc. Polycyclic aromatic hydrocarbons may react to form hydrogen and benzene or to form hydrogen and naphthalene. In order to produce the amount of hydrogen needed in the coal liquefaction step, temperature, pressure and reactants concentrations in the steam dealkylation zone are regulated according to the equilibrium conditions required in reactions between steam, carbon monoxide, carbon dioxide and hydrogen. The adjustment of conditions to produce the desired amount of hydrogen is within the ability of those skilled in the art from the foregoing description. In any case, the amount of hydrogen produced in the refining step is at least an amount sufficient to provide a hydrogen recycle stream which is passed to the coal liquefaction step to provide the complete hydrogen requirements for the coal liquefaction step and any hydrogen treatment performed on the coal liquids.

The effluent from the steam dealkylation zone is separated into a gaseous hydrogen-containing phase and a liquid hydrocarbons phase containing benzene and naphthalene. The gaseous phase is utilized to provide a hydrogen recycle stream which contains the total hydrogen requirements needed in the coal liquefaction step. The necessary separation between the liquids phase hydrocarbons and gases can conveniently be effected by passing the effluent from the steam dealkylation reactor into a condenser-separator. Steam in the gaseous phase is condensed and forms a separate liquid layer within the condenser-separator, and the hydrogen and any other gases such as carbon monoxide, carbon dioxide, methane, etc., remain in the gaseous phase. The gaseous phase is withdrawn from the condenserseparator, purified, if desirable, to remove gases other than hydrogen, and recycled to the liquefaction step to provide the hydrogen requirements thereof. The aromatic hydrocarbon products remain in the liquid phase in the condenser-separator, and form a hydrocarbons phase or layer, separate from the water layer therein. The aromatic hydrocarbon products of the process are then separated from the water phase by decantation, and further dried, purified and fractionated to separate and recover the valuable hydrocarbon components, primarily benzene.

The steam dealkylation catalysts which may be utilized in the refining step of the present process are known to those skilled in the art. It is to be emphasized that conventional hydrodealkylation catalysts are not suitable for use in the present process. This is apparent because hydrodealkylation necessarily consumes hydrogen in the dealkylation reaction rather than producing hydrogen, as is a necessary part of the operation of the present process. The steam dealkylation catalyst preferred for use in the present process is a composite containing a solid support and one or more metals. Suitable solids supports include the elements from Group Vlll of the Periodic Table and particularly rhodium, platinum, palladium and nickel. A preferred support includes a combination of aluminum and chromium, and a particularly preferred metal is rhodium. In addition, alkali metals, including sodium, potassium and lithium may be employed in the catalytic composite. A composite containing Pep, is particularly preferred in order to enhance the activity and stability of the catalyst for hydrogen production.

The alumina component of the preferred steam dealkylation catalyst is preferably characterized by a surface area of about I00 to about 300 square meters per gram. The alumina may suitably be prepared by the well known oil drop method. Reference may be made to US. Pat. No. 2,620,314 issued to James l-[oekstra for further details. When it is desired to utilize a chromia component, the chromia can be impregnated on the alumina, for example, by immersing the alumina in an aqueous solution of a suitable chromium compound such as chromium nitrate, which is then decomposed to chromia upon calcination. The alumina is immersed in the impregnating solution for a suitable period of time, while the excess water is evaporated or subsequently decanted. The procedure may be repeated without intermediate drying in order to achieve a chromia con tent in the catalyst of about 1 weight percent to about 60 weight percent and preferably of between about 5 weight percent and about 40 weight percent. Alternatively, the chromia may be incorporated with the alumina, initially, by the method described in column 2, lines 9-46 of US. Pat. No. 3,436,434, issued to George R. Lester. When it is desired to employ an alkali metal component, the alumina, or chromia alumina is treated with an aqueous solution of a suitable alkali metal salt such as lithium hydroxide, potassium nitrate, sodium hydroxide, etc. As in the chromia impregnation procedure, the impregnated carrier is then calcined to decompose the hydroxide or nitrate salt, etc. Suitable calcination temperature is between about 500C. and about 700C.

It is particularly desirable to add an m0, component to the catalyst. This can be done in the same mannet as the chromia and alkali metal impregnation procedures, by preparing an aqueous solution of a soluble iron compound. The iron component is conveniently impregnated in combination with a chromia and/or alkali metal component, both or all of which can be impregnated simultaneously from the same aqueous solution. Subsequently calcination will result in the formation of Fe,0,. When an Fe,0 component is employed in the steam dealkylation catalyst, it is used at a concentration of between about 0.2 weight percent to about 20 weight percent, based on the oxide.

After calcination of the alumina or chromia-alumina, along with alkali metal and/or Fe O the desired Group Vlll metal is implaced on the catalyst. It may be advantageous to steam treat the composite before incorporating the Group Vlll metal. This may be done by passing a steam-air mixture over the composite for about one hour to about 24 hours at a temperature of about 550C. to about 750C. The Group Vlll metal, preferably rhodium, is then incorporated by treating the alumina or chromia-alumina with an aqueous solution of a rhodium or other Group Vlll metal salt sufficient to provide a rhodium (or other Group Vlll metal) concentration of about 0.05 weight percent to about 2.5 weight percent.

Other steam dealkylation catalysts may also be employed in the refining step of the present process, but they may not necessarily give equivalent results.

ILLUSTRATIVE EMBODIMENT An lllinois bituminous coal is ground into particles sufficiently fine to pass through a 200 mesh Tyler sieve. The particulate coal is combined with tetrahydronaphthalene to form a colloidal suspension of coal in the solvent. A solvent/coal weight ratio of 2.5 to l is main- 9 tained. The coal-solvent mixture is passed into a conventional jacketed reactor at the rate of 600 grams per hour. A temperature of 450C. and a pressure of 140 atmospheres are maintained in the jacketed reactor. Three moles per hour of hydrogen gas, produced as described hereinafter, are also charged to the reactor continuously in admixture with the solvent and coal particles. A residence time for liquids and solid in the reactor of between about 30 and 60 minutes is maintained. The gaseous fraction of the effluent from the reactor is flash separated and recycled to the liquefaction reactor for further use along with fresh hydrogen produced in the refining step hereinafter described. The remaining solids in the liquefaction reactor effluent are separated from the liquid hydrocarbons phase in the effluent by filtration. The liquid hydrocarbons phase recovered is continuously charged to a conventional hydrogen treatment reactor and contacted therein with hydrogen produced as described hereinafter at the rate of about 0.15 mole to about 0.45 mole of hydrogen per kilogram of the liquid hydrocarbons phase to be processed in the reactor. A temperature of about 400C. to about 500C. and a hydrogen pressure of about 50 atmospheres to about 200 atmospheres are maintained in the hydrogen treatment reactor. Hydrogenation catalyst, comprising alumina composited with about weight percent cobalt and about 10 weight percent molybdenum, is admixed with the liquid hydrocarbons phase as a slurry and passed into the hydrogen treatment reactor at a catalyst/hydrocarbon weight ratio of from about 3 to about 8. A hydrocarbons residence time in the hydrogen treatment reactor of about 2 hours is maintained. The effluent from the hydrogen treatment reactor is settled and the catalyst is removed and recycled for further use in hydrogen treatment. The liquid hydrocarbons phase recovered from the effluent from the hydrogen treatment reactor is then passed to a conventional steam dealkylation reactor and commingled with steam at a steam/hydrocarbons weight ratio of about 20. The commingled steam and liquid hydrocarbons phase are charged to the conventional vertical tubular reactor, which contains a fixed bed of a steam dealkylation catalyst. The steam dealkylation catalyst has been prepared by steam treating alumina at 600C. for 12 hours, slurrying the treated alumina with an aqueous solution containing 16 weight percent chromia and 5.1 weight percent iron nitrate based on the alumina, evaporating the slurry to dryness, further drying at 250C, calcining at 650C, impregnating the resulting calcined composite with an aqueous solution containing about 5 weight percent potassium nitrate and about 2.2 weight percent rhodium chloride, drying the resulting composite and calcining at 550 for 2 hours. The liquid hydrocarbons phase is charged to the steam dealkylation reactor at a liquid hourly space velocity (based on the liquid hydrocarbons charged) of about 1.0. The steam dealkylation reactor temperature is maintained at 475C. and the pressure is maintained at about 20 atmospheres. The steam dealkylation reactor charge is passed in downward flow over the steam dealkylation catalyst bed. The steam dealkylation reactor effluent is separated into gaseous and liquid phases by passing the reactor effluent to a conventional condenser-separator. The gaseous phase recovered from the condenser-separator is treated to remove carbon oxides and methane. It is then analyzed and found to comprise substantially pure hydrogen. This hydrogen is passed to the liquefaction reactor at the rate of 3 moles per hour and is also passed to the hydrogen treatment reactor as needed. The liquid hydrocarbons phase and liquid water phase produced in the condenser-separator are separated by decantation and the water phase is discarded. The liquid hydrocarbons phase is dried and analyzed. It is found to comprise substantially pure benzene and naphthalene and is recovered as the product of the process.

1 claim as my invention:

1. 1n the liquefaction of coal by reaction thereof with hydrogen, the process which comprises separating from the products of the coal liquefaction a liquid comprising polycyclic aromatic, polycyclic hydroaromatic and alkylaromatic hydrocarbons, reacting sufficient amounts of said liquid and steam in contact with a dealkylation catalyst to form substantially all of the hydrogen required in the aforesaid coal liquefaction step, separating a hydrogen-containing gas from the resultant efi'luent and supplying to the coal liquefaction step a sufficient quantity of said gas to provide substantially all of the hydrogen requirements for the coal liquefaction.

2. The process of claim 1 wherein said coal is solvent extracted with a hydrocarbonaceous liquefaction solvent in said liquefaction step.

3. The process of claim 1 wherein said liquid and steam are reacted at a temperature of from about 650F. to about 1050F., a pressure of from about 1 atmosphere to about atmospheres and a weight ratio of steam to said liquid of from about 2:1 to about 30:1.

4. The process of claim 1 wherein said dealkylation catalyst comprises alumina having from about I to about 60 weight percent chromia and from about 0.01 to about 3 weight percent of a metal selected from rhodium, platinum and nickel composited therewith.

5. The process of claim 4 wherein said dealkylation catalyst contains from about 0.05'to about 2.5 weight percent rhodium and from about 0.1 to about 4 weight percent of an alkali metal, based on said alumina.

6. The process of claim 4 wherein said dealkylation catalyst contains from about 0.05 to about 2.5 weight percent rhodium and from about 0.2 to about 20 weight percent Fe,0,, based on said alumina.

I I 'l 0 l 

1. IN THE LIQUEFACTION OF COAL BY REACTION THEREOF WITH HYDROGEN, THE PROCESS WHICH COMPRISES SEPARATING FROM THE PRODUCTS OF THE COAL LIQUEFACTION A LIQUID COMPRISING POLYCYCLIC ATOMATIC, POLYCUCLIC HUDROAROMATIC AND ALKYLAROMATIC HYDROCARBONS, REACTING SUFFICIENT AMOUNTS OF SAID LIQUID AND STEAM IN CONTACT WITH A DEALKYLATION CATALYST TO FORM SUBSTANTIALLY ALL KOF THE HYDROGEN REQUIRED IN THE AFORESAID COAL LIQUEFACTION STEP, SEPATATING A HYDROGEN-CONTAINING GAS FROM THE RESULTANT EFFLUENT AND SUPPLYING TO THE COAL LIQUEFACTION STEP A SUFFICIENT QUANTITY OF SAID GAS TO PROVIDE SUBSTANTIALLY ALL OF THE HYDROGEN REQUIREMENTS FOR THE COAL LIQUEFACTION.
 2. The process of claim 1 wherein said coal is solvent extracted with a hydrocarbonaceous liquefaction solvent in said liquefaction step.
 3. The process of claim 1 wherein said liquid and steam are reacted at a temperature of from about 650*F. to about 1050*F., a pressure of from about 1 atmosphere to about 150 atmospheres and a weight ratio of steam to said liquid of from about 2:1 to about 30:1.
 4. The process of claim 1 wherein said dealkylation catalyst comprises alumina having from about 1 to about 60 weight percent chromia and from about 0.01 to about 3 weight percent of a metal selected from rhodium, platinum and nickel composited therewith.
 5. The process of claim 4 wherein said dealkylation catalyst contains from about 0.05 to about 2.5 weight percent rhodium and from about 0.1 to about 4 weight percent of an alkali metal, based on said alumina.
 6. The process of claim 4 wherein said dealkylation catalyst contains from about 0.05 to about 2.5 weight percent rhodium and from about 0.2 to about 20 weight percent Fe2O3, based on said alumina. 